1. Field of the Invention
The present invention relates to hot water heating devices, and more particularly, to open-to-atmosphere hot water heating and dispensing devices utilized, for example, adjacent the tap water dispenser in the domestic kitchen, for dispensing hot water at close to the boiling point.
2. Prior Art
Hot water heating and dispensing devices of the type to which the present invention relates are commonly used for providing hot water at close to the boiling point for preparation of hot beverages such as instant coffee and the like, and are generally well known in the prior art. For example, such devices are disclosed in U.S. Pat. No. 3,381,110 to Fisher and Karlen et al U.S. Pat. No. 2,869,760; and similarly in British Pat. No. 662,739. All of these devices include a small hot water tank which can be easily disposed underneath a counter top adjacent a sink and are provided with outlet conduits which can extend above the counter top over the sink for dispensing hot water at a much higher temperature than is available from the conventional tap which receives its hot water from the much larger central hot water heater disposed at a remote location from the sink.
Many such devices, including those mentioned above, have delt with the problem in such hot water dispensers of having an over flow of hot water out of the discharge or outlet conduit due to expansion of the water in the tank when it is heated. Such a discharge can be both annoying and cause minor damage to other equipment. For example, the dripping of hot water from the outlet conduit can cause discolorations in the sink in the form of sedimentary deposits left by the water.
It was recognized early in attempts to solve this problem that it is advantageous to provide an additional reservoir for allowing liquid displaced due to expansion to be accumulated in the reservoir rather than being forced out of the discharge conduit. It was also recognized that it was advantageous to place such a reservoir on the inlet side of the main tank. This is true for two reasons. First, it is preferable that the water which was displaced due to expansion is cold water and not water heated by the tank since this reduces the effect of sedimentation deposits in the opening to the reservoir from the main tank since it is well known that such sedimentation is enhanced by the high temperature. Second, it reduces energy losses which occur on such devices where hot water is expelled from the main tank into the reservoir and is thus permitted to cool and expel its heat to the atmosphere.
There are further variations in the manner in which such devices function. For example, the device disclosed in the above referred to U.S. Pat. No. 3,381,110 places an expansion chamber at the upper portion of the main heating tank at the level where the discharge conduit opens into the tank. By placing the reservoir at this position and connecting the reservoir with the inlet side of the water source to the tank, the cooler water in the bottom of the tank will be expelled through the inlet conduit to the reservoir as the water in the tank expands due to heating. As the water rises in the outlet conduit the additional volume of the reservoir will in essence act as an increased volume in the outlet conduit but will have cooler water in the reservoir rather than the hot water which is displaced from the top of the tank into the outlet conduit. Thus, in other words, the reservoir in such a device acts as an expansion reservoir which is only filled upon displacement of liquid due to expansion upon heating.
A further variation is disclosed in the above referred to British Pat. No. 662,739 in which an expansion tank is disposed in the inlet conduit to the main hot water heating tank, but is designed and connected to the inlet conduit to the hot water in the tank such that upon closing of the valve from the water supply source water will immediately return to the reservior from the main hot water heating tank. This manner of construction thus provides an open free volume at the top of the main tank which is sufficient to permit expansion of water in the tank due to heating without expelling water from the outlet conduit from which it is dispensed.
A further problem which has been recognized with such prior art devices is that if the water in such reservoirs is permitted to be exposed to air and is not utilized in a short period of time it will become stagnant, causing an undesirable taste in the water due to the inter action of the constituents in the water and the air with which it is in contact. It has been suggested that this problem can be overcome in one way, for example, as disclosed in the above referred to U.S. Pat. No. 3,381,110. This is by providing a flexible diaphragm which forms the top surface of the reservoir so that as water is displaced into the reservoir it will contact the diaphragm and thus eliminate the air space that will otherwise exist if a completely rigid reservoir were utilized.